Alternative Tertiary Structure of tRNA for Recognition by a Posttranscriptional Modification Enzyme

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• 作者：Ryuichiro Ishitani ; Osamu Nureki ; Nobukazu Nameki ; Norihiro Okada ; Susumu Nishimura and Shigeyuki Yokoyama
• 刊名：Cell
• 出版年：2003
• 出版时间：2 May 2003
• 年：2003
• 卷：113
• 期：3
• 页码：383-394
• 全文大小：1012 K

文摘

Transfer RNA (tRNA) canonically has the clover-leaf secondary structure with the acceptor, D, anticodon, and T arms, which are folded into the L-shaped tertiary structure. To strengthen the L form, posttranscriptional modifications occur on nucleotides buried within the core, but the modification enzymes are paradoxically inaccessible to them in the L form. In this study, we determined the crystal structure of tRNA bound with archaeosine tRNA-guanine transglycosylase, which modifies G15 of the D arm in the core. The bound tRNA assumes an alternative conformation ("λ form") drastically different from the L form. All of the D-arm secondary base pairs and the canonical tertiary interactions are disrupted. Furthermore, a helical structure is reorganized, while the rest of the D arm is single stranded and protruded. Consequently, the enzyme precisely locates the exposed G15 in the active site, by counting the nucleotide number from G1 to G15 in the λ form.